Method for connecting a blade to a hub and method for disconnecting a blade from a hub

ABSTRACT

A method for connecting a blade to a hub of a wind turbine, the method including pulling the blade towards the hub using a rope guided through an interior of the hub is provided. Thus, movements between the hub and the blade, in particular due to oscillations or waves, are reduced during the connection process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to PCT Application No.PCT/EP2020/069573, having a filing date of Jul. 10, 2020, which claimspriority to EP Application No. 19187812.3, having a filing date of Jul.23, 2019, the entire contents both of which are hereby incorporated byreference.

FIELD OF TECHNOLOGY

The following relates to a method for connecting a blade to a hub of awind turbine. Further, the following relates to a method fordisconnecting a blade from a hub of a wind turbine.

BACKGROUND

Wind turbines usually comprise a tower, a nacelle which is mounted tothe tower, a hub which is rotatably mounted to the nacelle, and rotorblades which are mounted to the hub.

Modern wind turbine rotor blades are built from fiber-reinforcedplastics. A rotor blade typically comprises an airfoil having a roundedleading edge and a sharp trailing edge. The rotor blade is connectedwith its blade root to the hub of the wind turbine. Further, the rotorblade is connected to the hub by a pitch bearing that allows a pitchmovement of the rotor blade.

In many cases, the rotor blades are transported to an erection site ofthe wind turbine for lifting and mounting the same to the hub once thehub is already mounted to the nacelle at the top of the tower.Therefore, a connection of the blades to the hub is usually made at anelevated height. This usually requires that a crane lifting the bladeessentially does not move relative to the hub. Thus, when connectingsuch a blade offshore, usually a jack up vessel must be provided whichprovides a rigid connection to the see ground.

SUMMARY

An aspect relates to a method for connecting a blade to a hub, and fordisconnecting the same from each other.

Accordingly, a method for connecting a blade to a hub of a wind turbineis provided. The method comprises pulling the blade towards the hubusing a rope guided through an interior of the hub.

Therefore, movements between the hub and the blade, in particular due tooscillations or waves, can be reduced during a connecting process. Thishas the advantage that the blade can be mounted to the hub offshore by avessel floating in water. Therefore, e.g., providing a jack up vesselcan be avoided.

“Rope” means a long element which is configured to transfer pullingforces and which cannot transfer compressive/pushing forces. Inparticular, the rope is a tension line, a cable, a belt, a chain and/ora wire. In particular, a tension is maintained in the rope. In anembodiment, the rope is pulled from the interior of the hub, inparticular by means of a winch or the like. “Guided through the interiorof the hub” means that at least one part of the rope is located in theinterior of the hub.

A “wind turbine” presently refers to an apparatus converting the wind'skinetic energy into rotational energy, which may again be converted toelectrical energy by the apparatus.

According to an embodiment, the method comprises the steps of

-   -   a) providing the hub which is mounted to a tower of the wind        turbine, b) providing the blade and the rope which is connected        to the blade with its one end, c) lifting the blade towards the        hub, d) placing the other end of the rope into the interior of        the hub, e) pulling the rope at the other end, and    -   f) connecting the blade to the hub.

In an embodiment, the rope is connected to a blade root with its oneend. In particular, the blade is lifted at a height of the hub in stepc). For example, the steps a)-f) are conducted in the listed order. Thehub is mounted to a nacelle which is mounted to the tower.

According to a further embodiment, the hub comprises a blade connectinginterface which has a hole to the interior of the hub, wherein the ropeis placed into the hole in step d).

This has the advantage that the blade can be pulled directly towards theblade connecting interface by the rope. In an embodiment, the hole is ahatch of the hub.

According to a further embodiment, the blade is pulled towards the hubin longitudinal direction of the blade.

This has the advantage that the blade is moved in connecting directionsuch that connecting means like pins or bolts can engage in respectiveopenings when moving the blade in the same movement direction. In anembodiment, the blade is pulled in horizontal direction. “Longitudinaldirection” means a direction pointing from a blade tip towards a radialcenter of the blade root.

According to a further embodiment, a movement of the blade perpendicularto the longitudinal direction of the blade is restricted by a firstguiding element.

This has the advantage that the blade can be hold close enough to thehub during blade connecting procedure even when extensive interferencefactors due to wind, waves and the like occur. “Perpendicular to thelongitudinal direction” means a radial and/or lateral direction.

According to a further embodiment, the first guiding element restrictsthe movement perpendicular to the longitudinal direction of the blade byengaging in the blade or the hub when the blade is moved towards the hub(first guiding step).

This has the advantage that a reliable restriction of the radialmovement can be provided. The first guiding element can be connected toone of the blade root and the hub. The other of the blade root and thehub comprises a receptacle for receiving the first guiding element.

According to a further embodiment, the first guiding element is aguiding cage connected to the hub and protruding from the hub, inparticular from the blade connecting surface (20).

In an embodiment the guiding cage is connected to the hub by springelements. This has the advantage that due to an elasticity of the springelement damage of the blade can be avoided when the blade hits the firstguiding element. For example, the spring element may be made of springsteel. The guiding cage may be a grid structure.

According to a further embodiment, the first guiding element has a tapershape.

This has the advantage that fitting the first guiding element into therespective receptacle is facilitated since the taper shape serves asinsertion slopes.

According to a further embodiment, a second guiding element restrictsthe movement perpendicular to the longitudinal direction of the blade byengaging in the first guiding element when the blade is moved towardsthe hub (second guiding step).

This has the advantage that the movement of the blade relative to thehub can be further restricted. In an embodiment, the second guidingelement engages into the first guiding element when the blade is closerto the hub compared to first guiding step. In particular, the secondguiding element is fixed to the blade root inside a cavity of the bladeroot.

According to a further embodiment, the second guiding element comprisesa tube connected to the blade, wherein the first guiding elementcomprises a receptacle for receiving the tube.

This has the advantage that a further mechanical guide is provided whichis robust and reliable. In an embodiment, the receptacle is an invertedcone. In an embodiment, the tube protrudes in longitudinal direction ofthe blade. In particular, the rope may extend through the tube. The tubemay also be termed a pipe. The tube or pipe may be formed from a rigidmaterial such as e.g., steel.

According to a further embodiment, the receptacle comprises insertionslopes for centering the second guiding element.

In particular, the insertions slopes guide the second guiding elementinto an insertion hole of the inverted cone. This has the advantage thatthe tube can be guided smoothly into the insertion hole.

According to a further embodiment, the movement of the bladeperpendicular to the longitudinal direction of the blade relative to thehub is restricted to less than 150 mm, 100 mm or 80 mm by the secondguiding element.

This has the advantage that a clearance between the blade and the hubcan be maintained small enough facilitating that the connecting stepsbetween the blade and the hub can be made.

“Restricted to less than 150 mm” may mean that a maximum movementdistance from one stop to an opposite stop is less than 150 mm.

According to a further embodiment, in step f) a plurality of pinsprotruding from a blade root are engaged in respective holes provided inthe hub.

When the pins penetrate the holes, e.g., the guiding steps are completedand no radial movements of the blade relative to the hub are possible.Therefore, a tight form-fit connection between the blade and the hub isprovided. The pins are for example bolts or part of a bolt connection.In an embodiment, the blade and the hub are screwed together.

According to a further embodiment, the rope is connected to the bladeinside a cavity in the blade, in particular the blade root.

In an embodiment, the cavity is open and thus accessible. This meansthat the cavity is penetrated by the first guiding element and that thecavity receives the first guiding element when the blade is movedtowards the hub.

According to a further embodiment, the blade is hold by a vesselfloating in water.

This has the advantage that a blade connecting process may be conductedwithout a jack up vessel and, thus, cost-efficient and/or in offshoreregions having a great water depth.

Further, a blade for a wind turbine is provided, the blade comprises ablade root and a rope which is connected to the blade root with its oneend such that the blade root can be pulled by a free end of the rope.

All embodiments and features explained with reference to the methodapply mutatis mutandis to the blade of embodiments of the presentinvention.

Furthermore, a method for disconnecting a blade from a hub of a windturbine is provided. The method comprises pulling the blade away fromthe hub, wherein a rope guided through the interior of the hub maintainsa tension between the hub and the blade.

All embodiments and features explained with reference to the method forconnecting the blade to the hub apply mutatis mutandis to the method fordisconnecting the blade from the hub of embodiments of the presentinvention.

Further possible implementations or alternative solutions of embodimentsof the invention also encompass combinations that are not explicitlymentioned herein of features described above or below with regard to theembodiments. The person skilled in the art may also add individual orisolated aspects and features to the most basic form of embodiments ofthe invention.

BRIEF DESCRIPTION

Some of the embodiments will be described in detail, with reference tothe following figures, wherein like designations denote like members,wherein:

FIG. 1 shows a perspective view of a wind turbine according to oneembodiment;

FIG. 2 shows a perspective view of a wind turbine blade of the windturbine according to FIG. 1 ;

FIG. 3 shows a schematic side view of the blade and the hub beforeconnecting the same together;

FIG. 4 shows a schematic longitudinal cut through the blade;

FIG. 5 shows a position of the blade when guided towards the hub;

FIG. 6 shows a position of the blade when guided towards the hub with areduced distance from FIG. 5 ,

FIG. 7 shows a position of the blade when guided towards the hub with areduced distance from FIG. 6 ;

FIG. 8 shows a schematic front view of a guiding element;

FIG. 9 shows a block diagram of a method for connecting the blade to thehub; and

FIG. 10 shows a block diagram of a method for disconnecting the bladefrom the hub.

DETAILED DESCRIPTION

FIG. 1 shows a wind turbine 1. The wind turbine 1 comprises a rotor 2connected to a generator (not shown) arranged inside a nacelle 3. Thenacelle 3 is arranged at an upper end of a tower 4 of the wind turbine1.

The rotor 2 comprises three blades 5 (i.e., wind turbine blades). Theblades 5 are connected to a hub 6 of the wind turbine 1. Rotors 2 ofthis kind may have diameters ranging from, for example, 30 to 300 metersor even more. The blades 5 are subjected to high wind loads. At the sametime, the blades 5 need to be lightweight. For these reasons, blades 5in modern wind turbines 1 are manufactured from fiber-reinforcedcomposite materials, e.g., by casting. Oftentimes, glass or carbonfibers in the form of unidirectional fiber mats are used. Such blades 5may also include woods and other reinforcement materials.

FIG. 2 shows one blade 5 from FIG. 1 . The blade 5 comprises anaerodynamically designed portion 7 which is shaped for optimumexploitation of the wind energy and a blade root 8 for connecting theblade 5 to the hub 6. Further, the blade 5 comprises a blade tip 9 whichfaces away from the blade root 8. The blade 5 extends in a longitudinaldirection L which points from the blade tip 9 towards the blade root 8.The wind turbine blade 5 comprises a leading edge 10 and a trailing edge11.

FIG. 3 shows a schematical side view of the blade 5 and the hub 6 beforeconnecting the same to each other. The blade 5 is lifted by a crane 12arranged on a vessel 13. The blade 5 is lifted to the same height H asthe hub 6 for connecting the same together. The blade root 8 comprisesan open cavity 14 (see broken lines) or an open hollow space. A rope 15is connected to the blade 5 inside the cavity 14 with its one end 16such that the blade root 8 can be pulled by a free end 17 of the rope15. A weight 18 can be provided at the free end 17. The rope 15 can beprovided as a tension line. In an embodiment, an auxiliary rope 19 isprovided for holding the rope 15 in a central position in the cavity 14.

The hub 6 comprises a blade connecting interface 20 for connecting thebade root 8 thereto. In an embodiment, the hub 6 comprises two furtherblade connecting interfaces (not shown). The blade connecting interface20 comprises a hole 21, in particular a hatch, to an interior 22 of thehub 6. Further, a guiding element 23 (also referred as first guidingelement) is connected to the blade connecting interface 20.

The guiding element 23 is configured to enter and engage the cavity 14.This means that the cavity 14 receives the guiding element 23 when theblade 5 is moved towards the hub 6. When doing so, a movementperpendicular to the longitudinal direction L, i.e., in radial directionR, of the blade 5 relative to the hub 6 is restricted. The cavity 14serves as a receptacle for receiving the guiding element 23 forming aform-fit in radial direction R. This has the advantage that a reliablerestriction of the radial movement can be provided.

For providing the movement of the blade 5 in longitudinal direction Lrelative to the hub 6, the free end 17 of the rope 15 is placed throughthe hole 21 into the interior 22 such that the rope 15 is guided throughthe interior 22 of the hub 6. The guiding element 23 is e.g., a guidingcage connected to the hub 6 and protruding from the hub 6. The guidingelement 23 is connected to the hub 6 by spring elements 24, for example.This has the advantage that due to an elasticity of the spring elements24 damage of the blade 5 can be avoided when the blade 5 hits theguiding element 23. The guiding element 23 may be a grid structure.

In an embodiment, the guiding element 23 has a taper shape. Inparticular, the guiding element 23 widens towards the blade connectinginterface 20. This has the advantage that fitting the cavity 14 onto theguiding element 23 is facilitated since the taper shape serves asinsertion slopes.

FIG. 4 shows a schematical longitudinal cut through the blade 5. Aguiding element 25 (also referred as second guiding element) isconnected to the blade 5 inside the cavity 14. In an embodiment, theguiding element 25 extends in longitudinal direction L. In particular,the guiding element 25 is a rod and/or probe. The guiding element 25 mayhave a centered alignment inside the cavity 14.

The guiding element 25 may comprise a hollow element 26, in particular atube, and a hollow element 27, in particular a tube, slidably supportingthe hollow element 26. A sliding movement may be limited by a stop 28arranged inside the hollow element 27. For example, the rope 15 mayextend through the hollow element 26 and the hollow element 27 and maybe fixed to the blade 5 or the hollow element 27 by a connecting point29, in particular anchor point. The hollow element 27 is connected tothe blade root 8 inside the cavity 14.

The rope 25 may extend from the guiding element 25 through a ring 30which is connected to the rope 19 and maintained in a central positioninside the cavity 14. The rope 19 is guided through a turning element31, in particular a guiding roller, and connected to the blade 5 by aconnecting point 32, in particular anchor point. The rope 19 may be anelastic line.

FIGS. 5 to 7 shows different positions of the blade 5 when guidedtowards the hub 6. The free end 17 of the rope 15 is guided through theinterior 22 of the hub 6. A force F pulls at the free end 17 such thatthe blade root 8 is moved towards the blade connecting interface 20 ofthe hub 6. The pulling force F may be provided e.g., by a winch (notshown).

Further, a plurality of pins 33, in particular bolts, protruding fromthe blade root 8 in longitudinal direction L are configured to engage inrespective holes 34 provided in the hub 6, in particular the bladeconnecting interface 20. The guiding element 25 is configured torestrict the movement of the blade 5 in radial direction R by engagingin the guiding element 23, in particular a receptacle 35 in the guidingelement 23, when the blade 5 is moved towards the hub 6. This has theadvantage that that a further mechanical guide is provided which isrobust and reliable. In an embodiment, the receptacle 35 is an invertedcone tapering towards the hub 6.

As shown in FIG. 5 the guiding element 23 does not engage into thecavity 14. When a distance D between the blade connecting interfaced 20and the blade root 8 is further reduced as shown in FIG. 6 the guidingelement 23 engages into the cavity 14 and restricts the relativemovement of the blade root 8 in radial direction R. When furtherreducing the distance D, the guiding element 25 is caught by thereceptacle 35 as shown in FIG. 7 . The receptacle 35 comprises insertionslopes 36 for catching and centering the guiding element 25. This hasthe advantage that the movement of the blade root 8 relative to the hub6 can be further restricted.

For example, the movement of the blade 5 in radial direction R relativeto the 6 hub is restricted to less than 150 mm, 100 mm or 80 mm when theguiding element 25 engages in the receptacle 35 (as shown in FIG. 7 ).This has the advantage that a clearance between the blade 5 and the hub6 can be maintained small enough for facilitating that the pins 33 canbe engaged into the holes 34.

When the pins 33 penetrate the holes 34, e.g., the guiding steps arecompleted and no radial movements of the blade 5 relative to the hub 6are possible. Therefore, a tight form-fit connection between the blade 5and the hub 6 is provided. The pins 33 are for example bolts or part ofa bolt connection. In an embodiment, the blade 5 and the hub 6 arescrewed together, in particular by the bolts and nuts connected to thebolts (not shown).

FIG. 8 shows a schematical front view of the guiding element 23. Theguiding element 23 comprises a circular base portion 37 (e.g., a ring),the receptacle 35 and, in particular fife, guiding portions 38 arrangedcircular and which connect the receptacle 35 to the base portion 37. Thereceptacle 35 comprises a central opening 39 (also referred as insertionhole) for being penetrated by the guiding element 25 and for guiding therope 15. The receptacle 35 has an open section 40 such that the opening39 is radially assessable.

FIG. 9 shows a block diagram of a method for connecting the blade 5 tothe hub 6. In step S1 the hub 6 which is mounted to the tower 4 of thewind turbine 1 is provided. In a step S2 the blade 5 and the rope 15which is connected to the blade 5 with its one end 16 is provided, inparticular by the vessel 13. In a step S3 the blade 5 is lifted towardsthe hub 6, in particular by the crane 12.

In step S4 the other end 17 of the rope 15 is placed into the interior22 of the hub 6. In a step S5 the blade 5 is pulled towards the hub 6using the rope 15 guided through the interior 22. In a step S6 theguiding element 23 penetrates the cavity 14 (first guiding step) suchthat radial movements of the blade root 8 are restricted by a firstclearance. In a step S7 the guiding element 25 penetrates the guidingelement 23 (second guiding step) such that the radial movements of theblade root 8 are restricted by a second clearance which is less than thefirst clearance.

Thus, the hub 6 and the blade 5 are brought close enough together by atwo-stage physical guide system. In a step S8 the pins 33 penetrate theholes 34. In a step S9 the blade 5 is connected the hub 6 by fixing thesame to each other. The step S5 can be conducted time and again duringsteps S6 to S8. The steps S1 to S9 (e.g., apart from step S5) areconducted in the listed order.

FIG. 10 shows a block diagram of a method for disconnecting the blade 5from the hub 6. The method comprising the step S11 of releasingconnecting means 33 between the blade 5 and the hub 6. In a step S12 theblade 5 is pulled away from the hub 5, in particular by the crane 12,wherein a rope 15 guided through the interior 22 of the hub 6 maintainstension between the hub 6 and the blade 5. This has the advantage thatthe blade 5 cannot slip away from the hub 6. Further, the guidingelements 23, 25 serve as restrictions movements in the radial directionR.

Although embodiments of the present invention have been described inaccordance with preferred embodiments, it is obvious for the personskilled in the art that modifications are possible in all embodiments.For example, all features described with reference to the FIGS. 1 to 9apply mutatis mutandis to a method for disconnecting the blade 5 fromthe hub 6 shown in FIG. 10 and vice versa.

Although the present invention has been disclosed in the form ofpreferred embodiments and variations thereon, it will be understood thatnumerous additional modifications and variations could be made theretowithout departing from the scope of the invention.

For the sake of clarity, it is to be understood that the use of “a” or“an” throughout this application does not exclude a plurality, and“comprising” does not exclude other steps or elements.

The invention claimed is:
 1. A method for connecting a blade to a hub ofa wind turbine, the method comprising: providing the hub mounted to atower of the wind turbine; providing the blade and a rope connected tothe blade at a first end; lifting the blade towards the hub; guiding asecond end of the rope into an interior of the hub; pulling the rope atthe second end and thereby pulling the blade towards the hub using therope guided into the interior of the hub; and connecting the blade tothe hub; wherein the blade is pulled towards the hub in a longitudinaldirection of the blade, wherein a movement of the blade perpendicular tothe longitudinal direction of the blade is restricted by a first guidingelement, wherein the first guiding element is a guiding cage connectedto the hub and protruding from the hub, and wherein the guiding cage hasa grid structure.
 2. The method according to claim 1, wherein the hubcomprises a blade connecting interface which has a hole to the interiorof the hub, and wherein the rope is placed into the hole as part ofguiding the second end of the rope into the interior of the hub.
 3. Themethod according to claim 1, wherein the first guiding element restrictsthe movement perpendicular to the longitudinal direction of the blade byengaging in the blade or the hub when the blade is moved towards thehub.
 4. The method according to claim 1, wherein the first guidingelement protrudes from the blade connecting surface.
 5. The methodaccording to claim 1, wherein the first guiding element has a tapershape.
 6. The method according to claim 3, wherein a second guidingelement restricts the movement perpendicular to the longitudinaldirection of the blade by engaging in the first guiding element when theblade is moved towards the hub.
 7. The method according to claim 6,wherein the second guiding element comprises a tube connected to theblade, and wherein the first guiding element comprises a receptacle forreceiving the tube.
 8. The method according to claim 7, wherein thereceptacle comprises insertion slopes for centering the second guidingelement.
 9. The method according to claim 7, wherein the movement of theblade perpendicular to the longitudinal direction of the blade relativeto the hub is restricted to less than 150 mm, 100 mm or 80 mm by thesecond guiding element.
 10. The method according to claim 1, whereinwhen connecting the blade to the hub a plurality of pins protruding froma blade root are engaged in respective holes provided in the hub. 11.The method according to claim 1, wherein the rope is connected to theblade inside a cavity in the blade.
 12. A method for disconnecting ablade from a hub of a wind turbine, the method comprising pulling theblade away from the hub, wherein a rope guided through an interior ofthe hub maintains a tension between the hub and the blade, wherein amovement of the blade perpendicular to a longitudinal direction of theblade is restricted by a first guiding element for at least a portion oftime, wherein the first guiding element is a guiding cage connected tothe hub and protruding from the hub, and wherein the guiding cage has agrid structure.
 13. A method for connecting a blade to a hub of a windturbine, the method comprising: providing the hub mounted to a tower ofthe wind turbine; providing the blade and a rope connected to the bladeat a first end; lifting the blade towards the hub; guiding a second endof the rope into an interior of the hub; pulling the rope at the secondend and thereby pulling the blade towards the hub using the rope guidedinto the interior of the hub; and connecting the blade to the hub;wherein the blade is pulled towards the hub in a longitudinal directionof the blade, wherein a movement of the blade perpendicular to thelongitudinal direction of the blade is restricted by a first guidingelement and a second guiding element, wherein the second guiding elementcomprises a tube connected to the blade, and wherein the first guidingelement comprises a receptacle for receiving the tube.
 14. The methodaccording to claim 13, wherein the receptacle comprises insertion slopesfor centering the second guiding element.
 15. The method according toclaim 13, wherein the movement of the blade perpendicular to thelongitudinal direction of the blade is restricted to less than 150 mm,100 mm, or 80 mm by the second guiding element.
 16. The method accordingto claim 13, wherein the first guiding element is a guiding cageconnected to the hub and protruding from the hub.